We study the end-to-end capacity of a cooperative relaying scheme using OFDM modulation, under power constraints for both the base station and the relay station. The relay uses an amplify-and-forward cooperative relaying technique to retransmit messages on a subset of the available subcarriers. The power used in the base station and the relay station transmitters is allocated in such a manner that the overall system capacity is maximized. The subcarrier selection and power allocation are obtained based on convex optimization formulations and an iterative algorithm. The proposed technique outperforms nonselective relaying schemes over a range of relay power budgets.

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This paper investigates a Decode-and-Forward (DF) two-hop relaying system in which Orthogonal Frequency Division Multiplexing (OFDM) is used. The relay forwards the message received from the source on a subset of available subchannels in the second time slot. Firstly, a pairing and selecting algorithm is proposed. Then, power will be allocated to the both base station and relay station under individual power constraints in order to maximize the capacity. The pairing and selecting algorithm and resource allocation is based on instantaneous channel state information (ICSI). Finally, the simulation results show that selective relaying combined with subcarrier pairing and power allocation will improve the system capacity to a considerable extent.

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